// Copyright 2015 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

import 'package:file/file.dart';
import 'package:file/local.dart';
import 'package:file/memory.dart';
import 'package:file/record_replay.dart';
import 'package:meta/meta.dart';

import 'common.dart' show throwToolExit;
import 'context.dart';
import 'platform.dart';
import 'process.dart';

export 'package:file/file.dart';
export 'package:file/local.dart';

const String _kRecordingType = 'file';
const FileSystem _kLocalFs = LocalFileSystem();

/// Currently active implementation of the file system.
///
/// By default it uses local disk-based implementation. Override this in tests
/// with [MemoryFileSystem].
FileSystem get fs => context.get<FileSystem>() ?? _kLocalFs;

/// Gets a [FileSystem] that will record file system activity to the specified
/// base recording [location].
///
/// Activity will be recorded in a subdirectory of [location] named `"file"`.
/// It is permissible for [location] to represent an existing non-empty
/// directory as long as there is no collision with the `"file"` subdirectory.
RecordingFileSystem getRecordingFileSystem(String location) {
  final Directory dir = getRecordingSink(location, _kRecordingType);
  final RecordingFileSystem fileSystem = RecordingFileSystem(
      delegate: _kLocalFs, destination: dir);
  addShutdownHook(() async {
    await fileSystem.recording.flush();
  }, ShutdownStage.SERIALIZE_RECORDING);
  return fileSystem;
}

/// Gets a [FileSystem] that replays invocation activity from a previously
/// recorded set of invocations.
///
/// [location] must represent a directory to which file system activity has
/// been recorded (i.e. the result of having been previously passed to
/// [getRecordingFileSystem]), or a [ToolExit] will be thrown.
ReplayFileSystem getReplayFileSystem(String location) {
  final Directory dir = getReplaySource(location, _kRecordingType);
  return ReplayFileSystem(recording: dir);
}

/// Create the ancestor directories of a file path if they do not already exist.
void ensureDirectoryExists(String filePath) {
  final String dirPath = fs.path.dirname(filePath);
  if (fs.isDirectorySync(dirPath)) {
    return;
  }
  try {
    fs.directory(dirPath).createSync(recursive: true);
  } on FileSystemException catch (e) {
    throwToolExit('Failed to create directory "$dirPath": ${e.osError.message}');
  }
}

/// Creates `destDir` if needed, then recursively copies `srcDir` to `destDir`,
/// invoking [onFileCopied], if specified, for each source/destination file pair.
///
/// Skips files if [shouldCopyFile] returns `false`.
void copyDirectorySync(
  Directory srcDir,
  Directory destDir, {
  bool shouldCopyFile(File srcFile, File destFile),
  void onFileCopied(File srcFile, File destFile),
}) {
  if (!srcDir.existsSync()) {
    throw Exception('Source directory "${srcDir.path}" does not exist, nothing to copy');
  }

  if (!destDir.existsSync()) {
    destDir.createSync(recursive: true);
  }

  for (FileSystemEntity entity in srcDir.listSync()) {
    final String newPath = destDir.fileSystem.path.join(destDir.path, entity.basename);
    if (entity is File) {
      final File newFile = destDir.fileSystem.file(newPath);
      if (shouldCopyFile != null && !shouldCopyFile(entity, newFile)) {
        continue;
      }
      newFile.writeAsBytesSync(entity.readAsBytesSync());
      onFileCopied?.call(entity, newFile);
    } else if (entity is Directory) {
      copyDirectorySync(
        entity,
        destDir.fileSystem.directory(newPath),
        shouldCopyFile: shouldCopyFile,
        onFileCopied: onFileCopied,
      );
    } else {
      throw Exception('${entity.path} is neither File nor Directory');
    }
  }
}

/// Gets a directory to act as a recording destination, creating the directory
/// as necessary.
///
/// The directory will exist in the local file system, be named [basename], and
/// be a child of the directory identified by [dirname].
///
/// If the target directory already exists as a directory, the existing
/// directory must be empty, or a [ToolExit] will be thrown. If the target
/// directory exists as an entity other than a directory, a [ToolExit] will
/// also be thrown.
Directory getRecordingSink(String dirname, String basename) {
  final String location = _kLocalFs.path.join(dirname, basename);
  switch (_kLocalFs.typeSync(location, followLinks: false)) {
    case FileSystemEntityType.file:
    case FileSystemEntityType.link:
      throwToolExit('Invalid record-to location: $dirname ("$basename" exists as non-directory)');
      break;
    case FileSystemEntityType.directory:
      if (_kLocalFs.directory(location).listSync(followLinks: false).isNotEmpty) {
        throwToolExit('Invalid record-to location: $dirname ("$basename" is not empty)');
      }
      break;
    case FileSystemEntityType.notFound:
      _kLocalFs.directory(location).createSync(recursive: true);
  }
  return _kLocalFs.directory(location);
}

/// Gets a directory that holds a saved recording to be used for the purpose of
/// replay.
///
/// The directory will exist in the local file system, be named [basename], and
/// be a child of the directory identified by [dirname].
///
/// If the target directory does not exist, a [ToolExit] will be thrown.
Directory getReplaySource(String dirname, String basename) {
  final Directory dir = _kLocalFs.directory(_kLocalFs.path.join(dirname, basename));
  if (!dir.existsSync()) {
    throwToolExit('Invalid replay-from location: $dirname ("$basename" does not exist)');
  }
  return dir;
}

/// Canonicalizes [path].
///
/// This function implements the behavior of `canonicalize` from
/// `package:path`. However, unlike the original, it does not change the ASCII
/// case of the path. Changing the case can break hot reload in some situations,
/// for an example see: https://github.com/flutter/flutter/issues/9539.
String canonicalizePath(String path) => fs.path.normalize(fs.path.absolute(path));

/// Escapes [path].
///
/// On Windows it replaces all '\' with '\\'. On other platforms, it returns the
/// path unchanged.
String escapePath(String path) => platform.isWindows ? path.replaceAll('\\', '\\\\') : path;

/// Returns true if the file system [entity] has not been modified since the
/// latest modification to [referenceFile].
///
/// Returns true, if [entity] does not exist.
///
/// Returns false, if [entity] exists, but [referenceFile] does not.
bool isOlderThanReference({ @required FileSystemEntity entity, @required File referenceFile }) {
  if (!entity.existsSync()) {
    return true;
  }
  return referenceFile.existsSync()
      && referenceFile.statSync().modified.isAfter(entity.statSync().modified);
}

/// Exception indicating that a file that was expected to exist was not found.
class FileNotFoundException implements IOException {
  const FileNotFoundException(this.path);

  final String path;

  @override
  String toString() => 'File not found: $path';
}

/// Reads the process environment to find the current user's home directory.
///
/// If the searched environment variables are not set, '.' is returned instead.
String userHomePath() {
  final String envKey = platform.operatingSystem == 'windows' ? 'APPDATA' : 'HOME';
  return platform.environment[envKey] ?? '.';
}